Use of siloxane copolymers comprising alkenyl groups as antimisting additives in cross-linkable silicone coating compositions

ABSTRACT

Branched, alkenyl-functional organopolysiloxanes prepared by reacting an organic compound having at least two aliphatic double bonds with an organopolysiloxane having more than one Si-bonded hydrogen atom, in the presence of a hydrosilylation catalyst, and in a stoichiometric ratio of aliphatic double bonds to Si-bonded hydrogen such that an alkenyl-functional product is obtained, function as highly effective antimisting additives in the high speed coating of substrates with crosslinkable silicone compositions.

The invention relates to the use of antimisting additives for reducingthe formation of aerosol in crosslinkable silicone coating compositions.

A trend within the silicone coating industry is to increase machinespeed in order to raise productivity. Where silicone coatings areapplied to the substrate at relatively high speeds, of more than 300m/min, for example, fine spray mists of the silicone coating system maybe formed. This aerosol is formed at the silicone applicator unit. Theformation of this spray mist proves to be a serious problem in thecontext of further increases in the coating speed.

The formation of this spray mist can be reduced by adding what are knownas antimisting additives to the silicone coating system.

EP-A 716 115 (Dow Corning Corp.) describes antimisting additivesobtained by reacting an organosilicon compound, a compound containingoxyalkylene groups, and a catalyst. The addition of theseoxyalkylene-functional reaction products to crosslinkable siliconecoating systems reduces the formation of aerosol in rapid coatingprocesses.

WO 01/98420 (Dow Corning Corp.) discloses a liquid silicone antimistingcomposition, which is obtained by reacting

-   a) an organohydropolysiloxane having at least two Si—H groups (SiH)    with-   b) an organoalkenylsiloxane having at least three alkenyl groups    (C═C) in-   c) the presence of a platinum catalyst and if desired-   d) an inhibitor-   in a ratio of C═C/SiH≧4.6.

An extremely large excess of organoalkenylsiloxane (C═C) is necessary inorder to prevent gelling. This excess influences the release propertiesof the base system, the crosslinkable silicone coating composition.Furthermore, an inhibitor has to be added to prevent gelling.

U.S. Pat. No. 5,241,034 (Wacker-Chemie GmbH) describes alkenylfunctional siloxane copolymers which are branched and whoseorganopolysiloxane blocks are linked by hydrocarbon bridges.

The object was to provide antimisting additives for silicone coatingcompositions which reduce the formation of aerosol in rapid coatingprocesses, which are readily miscible with the silicone coatingcompositions, and which do not impair the silicone coating compositions.This object is achieved by the invention.

The invention provides for the use of antimisting additives incrosslinkable silicone coating compositions for reducing the formationof aerosol, characterized in that as antimisting additivesalkenyl-functional siloxane copolymers containing

-   (a) siloxane units of the formula $\begin{matrix}    {R_{a}{{Si}\left( {OR}^{1} \right)}{{}_{}^{}{}_{{4 - \left( {a + b} \right)}2}^{}}} & (I)    \end{matrix}$    -   where    -   R is identical or different, unhalogenated or halogenated        hydrocarbon radicals having from 1 to 18 carbon atoms per        radical,    -   R¹ is identical or different alkyl radicals having from 1 to 4        carbon atoms per radical, which may be substituted by an ether        oxygen atom,    -   a is 0, 1, 2 or 3,    -   b is 0, 1, 2 or 3    -   and the sum a+b is not greater than 3,-   (b) per molecule at least one siloxane unit of the formula    $\begin{matrix}    {{A{Si}R}_{c}{SiO}_{\frac{4 - {({c + 1})}}{2}}} & ({II})    \end{matrix}$    -   where    -   R is as defined above,    -   c is 0, 1 or 2,    -   A is a radical of the formula        —CH₂CHR³—R²(CR³═CH₂)_(x-1)        where    -   R² is a divalent, trivalent or tetravalent hydrocarbon radical        having from 1 to 25 carbon atoms per radical,    -   R³ is a hydrogen atom or an alkyl radical having from 1 to 6        carbon atoms per radical, and    -   x is 2, 3 or 4, and-   (c) per molecule on average at least one unit selected from the    group consisting of units of the formulae where R and c are as    defined above, $\begin{matrix}    {{{O_{\frac{4 - {({c + 1})}}{2}}R_{c}{Si}} - A^{1} - {{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}},} & ({III}) \\    \begin{matrix}    {{{O_{\frac{4 - {({c + 1})}}{2}}R_{c}{Si}} - A^{2} - {{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}},} \\    | \\    {\quad{{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}}    \end{matrix} & ({IV}) \\    {\begin{matrix}    {\quad{{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}} \\    | \\    {{O_{\frac{4 - {({c + 1})}}{2}}R_{c}{Si}} - A^{3} - {{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}} \\    | \\    {\quad{{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}}    \end{matrix},} & (V)    \end{matrix}$    -   A¹ is a radical of the formula    -   where    -   R², R³ and x are as defined above,    -   A² is a radical of the formula    -   where    -   R², R³ and x are as defined above, with the proviso that R² is        not a divalent hydrocarbon radical, and    -   A³ is a radical of the formula        -   where        -   R² and R³ are as defined above, with the proviso that R² is            not a divalent or trivalent hydrocarbon radical.

Preferred alkenyl-functional siloxane copolymers are those containing

-   (a) siloxane units of the formula    R₂SiO  (I′),-   (b) per molecule on average more than one siloxane unit of the    formula    AR₂SiO_(1/2)  (II′) and-   (c) per molecule on average at least one unit selected from the    group consisting of units of the formulae    -   where    -   R, A, A¹ and A² are as defined above.

With particular preference the alkenyl-functional siloxane copolymerscontain per molecule on average at least two siloxane units of theformula (II′).

The invention also provides for the use of antimisting additives incrosslinkable silicone coating compositions for reducing the formationof aerosol, which comprises using as antimisting additivesalkenyl-functional siloxane copolymers preparable.

-   by reacting organic compound (1) containing at least two aliphatic    double bonds, of the general formula    R²(CR³═CH₂)_(x),    where-   R² is a divalent, trivalent or tetravalent hydrocarbon radical    having from 1 to 25 carbon atoms per radical,-   R³ is a hydrogen atom or an alkyl radical having from 1 to 6 carbon    atoms per radical, and-   x is 2, 3 or 4-   with organopolysiloxane (2) having on average more than one    Si-bonded hydrogen atom per molecule-   in the presence of catalyst (3) which promotes the addition of    Si-bonded hydrogen onto aliphatic double bond,-   the ratio of aliphatic double bond in organic compound (1) to    Si-bonded hydrogen in the organopolysiloxane (2) being such that    alkenyl-functional siloxane copolymers having on average more than    one alkenyl group per molecule, of the formula    —CR³═CH₂,    where-   R3 is as defined above, are obtained.

In the process according to the invention, alkenyl-functional siloxanecopolymers having on average at least four alkenyl groups per molecule,of the formula—CR³═CH₂,preferably on average at least eight alkenyl groups per molecule, of theformula—CR³═CH₂,where

-   R³ is as defined above,-   are preferably obtained.

The alkenyl-functional siloxane copolymers and their preparation aredescribed in the above-cited U.S. Pat. No. 5,241,034, and U.S. Pat. No.5,241,034 (incorporated by reference) is therefore part of thedisclosure content of this specification.

The antimisting additives of the invention, the alkenyl-functionalsiloxane copolymers, have the advantage that they not only reduce theformation of aerosol by crosslinkable silicone coating compositions inrapid coating systems but also, in particular, can be mixed in anydesired proportions, homogeneously, with the crosslinkable siliconecoating compositions, unlike the antimisting additives containingpolyglycol groups from the above-cited EP-A 716 115.

Moreover, the antimisting additives of the invention have no inhibitingeffect and they are storage-stable. The antimisting additives accordingto the invention have the advantage that they can be mixed beforehandwith the polymer component (A) of the crosslinkable silicone coatingcomposition. They are consequently easy to handle and do not impair therelease properties of the base system, the crosslinkable siliconecoating composition.

The alkenyl-functional siloxane copolymers of the invention preferablypossess a viscosity of from 500 to 5 000 000 mPa·s at 25° C., morepreferably from 1000 to 1 000 000 mPa·s at 25° C.

In the alkenyl-functional siloxane copolymers according to the inventionthe siloxane blocks are joined to one another via hydrocarbon groups,resulting in a hydrocarbon-siloxane block structure. Preferably the sumof the hydrocarbon groups A, A¹, A² and A³ in the alkenyl-functionalsiloxane copolymers is from 0.1 to 10% by weight, more preferably from0.1 to 2% by weight, based in each case on the total weight of thealkenyl-functional siloxane copolymers.

The polyaddition process of the invention results automatically in apolymer distribution in respect of the siloxane blocks and of thehydrocarbon blocks. A “polyadduct” of this kind usually also containslower oligomers, which also include adducts consisting only of onesiloxane block and two hydrocarbon blocks.

Examples of radicals R are alkyl radicals, such as the methyl, ethyl,n-propyl, isopropyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl,n-pentyl, isopentyl, neopentyl, tert-pentyl radical; hexyl radicals,such as the n-hexyl radical; heptyl radicals, such as the n-heptylradical; octyl radicals, such as the n-octyl radical and isooctylradicals, such as the 2,2,4-trimethylpentyl radical; nonyl radicals,such as the n-nonyl radical, decyl radicals, such as the n-decylradical; dodecyl radicals, such as the n-dodecyl radical; octadecylradicals, such as the n-octadecyl radical; cycloalkyl radicals, such ascyclopentyl, cyclohexyl, cycloheptyl radicals and methylcyclohexylradicals; aryl radicals, such as the phenyl, naphthyl, anthryl andphenanthryl radical; alkaryl radicals, such as o-, m-, p-tolyl radicals,xylyl radicals and ethylphenyl radicals and aralkyl radicals, such asthe benzyl radical, the α- and the β-phenylethyl radical. The methylradical is preferred.

Examples of halogenated radicals R are haloalkyl radicals, such as the3,3,3-trifluoro-n-propyl radical, the 2,2,2,2′,2′,2′-hexafluoroisopropylradical, the heptafluoroisopropyl radical and haloaryl radicals, such asthe o-, m-, and p-chlorophenyl radical.

Examples of alkyl radicals R¹ are the methyl, ethyl, n-propyl,isopropyl, 1-n-butyl, 2-n-butyl, isobutyl and tert-butyl radical. Themethyl and ethyl radicals are preferred. Examples of alkyl radicals R¹which are substituted by an ether oxygen atom are the methoxyethyl andethoxyethyl radical.

Examples of alkyl radicals R³ are the methyl, ethyl, n-propyl,isopropyl, 1-n-butyl, 2-n-butyl, isobutyl, tert-butyl, n-pentyl,isopentyl, neopentyl, tert-pentyl radical, and hexyl radicals, such asthe n-hexyl radical. R³ is preferably a hydrogen atom.

Examples of organic compound (1) containing at least two aliphaticdouble bonds which is used in the process according to the invention are

-   1,5-hexadiene,-   1,7-octadiene,-   1,9-decadiene,-   1,11-dodecadiene,-   1,13-tetradecadiene,-   3,5-dimethyl-1,6-heptadiene,-   3,5-dimethyl-4-vinyl-1,6-heptadiene,-   1,2,4-trivinylcyclohexane,-   1,3,5-trivinylcyclohexane,-   1,4-divinylbenzene and-   1,2,3,4-tetravinylcyclobutane,-   preference being given to 1,2,4-trivinylcyclohexane and    1,5-hexadiene.

Examples of the radical R² are therefore those of the formula

preference being given to the radicals of the formula

The organopolysiloxanes (2) used in the process according to theinvention preferably contain on average at least 1.5 Si-bonded hydrogenatoms, more preferably on average at least two Si-bonded hydrogen atomsper molecule.

With particular preference the organopolysiloxanes (2) used in theprocess according to the invention contain from two to four Si-bondedhydrogen atoms per molecule.

In the process according to the invention it is possible to use one kindof organopolysiloxane (2) or different kinds of organopolysiloxane (2).As a result of their preparation the organopolysiloxanes (2) are alsomixtures; in other words, for example, organopolysiloxanes having twoSi-bonded hydrogen atoms per molecule also contain organopolysiloxaneshaving only one Si-bonded hydrogen atom per molecule.

As organopolysiloxanes (2) it is preferred to use those of the generalformula $\begin{matrix}{{R_{e}H_{f}{SiO}_{\frac{4 - e - f}{2}}},} & ({VI})\end{matrix}$where

-   R is as defined above,-   e is 0 or 1, on average from 0.005 to 1.0,-   f is 0, 1, 2 or 3, on average from 1.0 to 2.0, and-   the sum e+f is not greater than 3,-   in the process according to the invention.

As organopolysiloxanes (2) it is more preferred to use those of thegeneral formulaH_(d)R_(3-d)SiO(SiR₂O)O(SiRHO)_(p)SiR_(3-d)H_(d)  (VII)where

-   R is as defined above,-   d is 0 or 1,-   o is 0 or an integer from 1 to 1000, and-   p is 0 or an integer from 1 to 6,    in the process according to the invention.

The organopolysiloxanes (2) preferably possess a viscosity of from 50 to20 000 mPa·s at 25° C., more preferably from 500 to 10 000 mPa·s·s at25° C.

Preferred examples of organopolysiloxanes of the formula (VII) arecopolymers of dimethylhydrosiloxane and dimethylsiloxane units,copolymers of dimethyl-hydrosiloxane, dimethylsiloxane andmethylhydrosiloxane units, copolymers of trimethylsiloxane andmethyl-hydrosiloxane units, and copolymers of trimethylsiloxane,dimethylsiloxane, and methylhydrosiloxane units.

Processes for preparing organopolysiloxanes having at least twoSi-bonded hydrogen atoms per molecule, including those of the preferredkind, are general knowledge.

In the case of the process according to the invention it is preferred touse as organic compound (I) 1,2,4-trivinylcyclohexane and asorganopolysiloxane (2) a siloxane of the general formulaHR₂SiO(SiR₂O)_(o)SiR₂Hwhere

-   R is as defined above and-   o is an integer from 50 to 1000.

Organic compound (1) is used in the process according to the inventionin amounts such that the ratio employed of aliphatic double bond inorganic compound (1) to Si-bonded hydrogen in organopolysiloxane (2) ispreferably from 1.1:1 to 20:1, more preferably from 1.5:1 to 10:1, verypreferably from 1.5:1 to 5:1, in particular from 1.5:1 to 3.0:1.

As catalysts which promote the addition of Si-bonded hydrogen ontoaliphatic multiple bond it is possible in the process of the inventionas well to use the same catalysts which it has also been possible todate to use for promoting the addition of Si-bonded hydrogen ontoaliphatic multiple bond. The catalysts are preferably a metal from thegroup of the platinum metals or a compound or a complex from the groupof the platinum metals. Examples of such catalysts are metallic andfinely divided platinum, which may be on supports, such as silica,alumina or activated carbon, compounds or complexes of platinum, such asplatinum halides, e.g., PtCl₄, H₂PtCl₆*6H₂O, Na₂PtCl₄*4H₂O,platinum-olefin complexes, platinum-alcohol complexes, platinum-alkoxidecomplexes, platinum-ether complexes, platinum-aldehyde complexes,platinum-ketone complexes, including reaction products of H₂PtCl₆*6H₂Oand cyclohexanone, platinum-vinylsiloxane complexes, such asplatinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexes with orwithout a detectable inorganically bonded halogen content,bis(gamma-picoline)platinum dichloride, trimethylenedipyridineplatinumdichloride, dicyclopentadieneplatinum dichloride,dimethyl-sulfoxide-ethyleneplatinum(II) dichloride,cyclooctadieneplatinum dichloride, norbornadieneplatinum dichloride,gamma-picolineplatinum dichloride, cyclopentadieneplatinum dichloride,and reaction products of platinum tetrachloride with olefin and primaryamine or secondary amine or primary and secondary amine, such as thereaction product of platinum tetrachloride dissolved in 1-octene withsec-butylamine or ammonium-platinum complexes.

The catalyst (3) is used preferably in amounts of from 0.5 to 1000 ppmby weight (parts by weight per million parts by weight), more preferablyin amounts of from 2 to 50 ppm by weight, calculated in each case aselemental platinum and based on the overall weight of organic compound(1) and organopolysiloxane (2).

The process according to the invention is preferably conducted at thepressure of the surrounding atmosphere, i.e., approximately at 1020 hPa(abs.), but may also be conducted at higher or lower pressures.Furthermore, the process according to the invention is conductedpreferably at a temperature of from 20° C. to 150° C., more preferablyfrom 20° C. to 80° C.

Since the organic compound (1) containing at least two aliphatic doublebonds, e.g., 1,2,4-trivinylcyclohexane, tends toward polymerization atrelatively high temperatures, it is possible in the process according tothe invention to use radical inhibitors, such as 4-methoxyphenol,2,6-bis(tert-butyl)-4-methylphenol, phenothiazine, hydroquinone orpyrocatechol. The radical inhibitors are used preferably in amounts offrom 10 to 500 ppm by weight, based on the overall weight of organiccompound (1) and organopolysiloxane (2).

In the process according to the invention it is possible to use inertorganic solvents, although the use of inert organic solvents is notpreferred. Examples of inert organic solvents are toluene, xylene,octane isomers, butyl acetate, 1,2-dimethoxyethane, tetrahydrofuran, andcyclohexane.

The alkenyl-functional siloxane copolymers prepared according to theprocess according to the invention preferably have their excess organiccompound (1) and also any inert organic solvent used removed bydistillation.

Alternatively to organic solvents it is possible to use inert siliconeoils in the process according to the invention or to trade the organicsolvent for such oils after the preparation of the branched siloxanecopolymers of the invention.

For greater ease of handling it is also possible to trade organicsolvents for reactive silicone oils after the preparation of thebranched siloxane copolymers of the invention, by adding such oils tothe reaction mixture and then removing the solvent by distillation.Preference is given to silicone oils having a viscosity of 100 mm²/s at25° C. and SiC-bonded alkenyl radicals as reactive constituent.

The alkenyl-functional siloxane copolymers prepared according to theprocess according to the invention are optionally equilibrated withorganopolysiloxane (4).

As organopolysiloxanes (4) it is preferred to use those selected fromthe group consisting of preferably linear organopolysiloxanes containingterminal triorganosiloxy groups, of the formulaR₃SiO(SiR₂O)_(r)SiR₃,where

-   R is as defined above and-   r is 0 or an integer whose value is preferably from 1 to 1500, more    preferably from 10 to 300,-   linear organopolysiloxanes containing terminal hydroxyl groups, of    the formula    HO(SiR₂O)_(s)H    where-   R is as defined above and-   s is an integer whose value is preferably from 1 to 1500,-   more preferably from 10 to 300,-   branched organopolysiloxanes optionally containing hydroxyl groups,    comprising units of the formula    R₃SiO_(1/2), R₂SiO and RSiO_(3/2)    where-   R is as defined above,-   cyclic organopolysiloxanes of the formula    (R₂SiO)_(t)    where-   R is as defined above and-   t is an integer from 3 to 12,-   and copolymers comprising units of the formula    R₂SiO and RSiO_(3/2)    where-   R is as defined above.

Preferred organopolysiloxanes (4) are preferably those of the formulaeR₃SiO(SiR₂O)_(r)SiR₃, HO(SiR₂O)_(s)H and (R₂SiO)_(t), particularpreference being given to those of the formula R₃SiO(SiR₂O)_(r)SiR₃.

The proportion of the organopolysiloxanes (4) used in the optionalequilibration and alkenyl-functional siloxane copolymers is determinedmerely by the desired fraction of the alkenyl groups in the siloxanecopolymers produced in the course of the optional equilibration, and bythe desired average chain length.

In the course of the optional equilibration, it is preferred to usebasic or acidic catalysts which promote the equilibration. Examples ofbasic catalysts are preferably alkali metal hydroxides, such as sodiumhydroxide, potassium hydroxide, and cesium hydroxide,trimethylbenzylammonium hydroxide, and tetramethylammonium hydroxide.Alkali metal hydroxides are preferred. Alkali metal hydroxides are usedpreferably in amounts of from 50 to 10 000 ppm by weight (=parts permillion), in particular from 500 to 2000 ppm by weight, based in eachcase on the overall weight of the alkenyl-functional siloxane copolymersand organopolysiloxanes (4) used.

Examples of acidic catalysts are preferably sulfuric acid, phosphoricacid, trifluoromethanoic acid, phosphorus nitride chlorides, and acidiccatalysts which are solid under the reaction conditions, such asacid-activated bleaching earth, acidic zeolites, sulfonated charcoal,and sulfonated styrene-divinylbenzene copolymer. Phosphorus nitridechlorides are preferred. Phosphorus nitride chlorides are usedpreferably in amounts of from 5 to 1000 ppm by weight (=parts permillion), in particular from 50 to 200 ppm by weight, based in each caseon the overall weight of the organosilicon compounds used.

The optional equilibration is conducted preferably at from 100° C. to150° C. and under the pressure of the surrounding atmosphere, i.e.,approximately at 1020 hPa (abs.). If desired, however, it is alsopossible to employ higher or lower pressures. The equilibration ispreferably conducted in from 5 to 20% by weight, based on the overallweight of the respective alkenyl-functional siloxane copolymers andorganopolysiloxanes (4) used, in water-immiscible solvent, such astoluene. The catalyst can be deactivated before the equilibrationmixture is worked up.

The process of the invention can be conducted batchwise,semicontinuously or fully continuously.

As antimisting additives it is preferred to use those alkenyl-functionalsiloxane copolymers which are prepared without a further equilibrationstep and have a particularly high level of branching. Preferredadditives are obtained from operating in the particularly preferredstoichiometric ranges indicated.

For reducing the formation of aerosol the antimisting additives of theinvention are added to the crosslinkable silicone coating compositions.

The antimisting additives of the invention, the alkenyl-functionalsiloxane copolymers, are used in the crosslinkable silicone coatingcompositions preferably in amounts of from 0.5 to 10% by weight, morepreferably from 1 to 5% by weight, based on the overall weight of thecrosslinkable silicone coating compositions.

As crosslinkable silicone coating compositions it is preferred to usethose comprising

-   (A) organosilicon compounds having radicals containing aliphatic    carbon-carbon multiple bonds,-   (B) organosilicon compounds containing Si-bonded hydrogen atoms,-   (C) catalysts which promote the addition of Si-bonded hydrogen onto    aliphatic multiple bond,    and if desired-   (D) inhibitors.

The invention further provides crosslinkable silicone coatingcompositions featuring reduced aerosol formation, comprising

-   (X) antimisting additives of the invention,-   (A) organosilicon compounds having radicals containing aliphatic    carbon-carbon multiple bonds,-   (B) organosilicon compounds containing Si-bonded hydrogen atoms,-   (C) catalysts which promote the addition of Si-bonded hydrogen onto    aliphatic multiple bond,    and if desired-   (D) inhibitors.

For the crosslinkable silicone coating compositions it is possible withpreference to use one kind of the antimisting additive (X) of theinvention or different kinds of the antimisting additive (X) of theinvention.

As organopolysiloxanes (A) having radicals containing aliphaticcarbon-carbon multiple bonds it is preferred to use linear or branchedorganopolysiloxanes comprising units of the general formula$\begin{matrix}{{R_{z}^{5}R_{y}^{6}{SiO}_{\frac{4 - z - y}{2}}},} & ({VIII})\end{matrix}$where

-   R⁵ is a monovalent, unsubstituted or substituted, hydrocarbon    radical having from 1 to 18 carbon atoms per radical and being free    from aliphatic carbon-carbon multiple bonds and-   R⁶ is a monovalent hydrocarbon radical having from 2 to 8 carbon    atoms per radical and containing a terminal aliphatic carbon-carbon    multiple bond,-   z is 0, 1, 2 or 3,-   y is 0, 1 or 2-   and the sum z+y is 0, 1, 2 or 3,-   with the proviso that there are on average at least 1.5 radicals R⁶,    preferably on average at least 2 radicals R⁶.

Preferred organosilicon compounds (A) are organopolysiloxanes of thegeneral formulaR⁶ _(g)R⁵ _(3-g)SiO(SiR⁵ ₂O)_(v)(SiR⁵R⁶O)_(w)SiR⁵ _(3-g)R⁶ _(g)  (IX)where

-   R⁵ and R⁶ are as defined above,-   g is 0, 1 or 2,-   v is 0 or an integer from 1 to 1500, and-   w is 0 or an integer from 1 to 200,-   with the proviso that on average at least 1.5 radicals R⁶,-   preferably on average at least 2 radicals R⁶, are present.

In the context of this invention formula (IX) is to be understood tomean that v units —(SiR⁵ ₂O)— and w units —(SiR⁵R⁶O)— may be distributedarbitrarily in the organopolysiloxane molecule.

As organosilicon compounds (A) it is also possible to use branchedpolymers containing terminal ω-alkenyl groups, preferably Si-bondedvinyl groups, as described in U.S. Pat. No. 6,034,225 (incorporated byreference), especially column 1 line 43 to column 2 line 13, and U.S.Pat. No. 6,258,913 (incorporated by reference), especially column 1 line62 to column 2 line 35.

As organosilicon compounds (A) it is also possible to use linearorganopolysiloxanes as described in U.S. Pat. No. 6,274,692(incorporated by reference), especially column 2 lines 3 to 27, which donot have an aliphatically unsaturated hydrocarbon radical, such as anSi-bonded vinyl group, at both ends but instead also have aliphaticallysaturated hydrocarbon radicals, such as Si-bonded methyl groups, at theends.

As organosilicon compounds (A) it is also possible to use those asdescribed in DE-A 195 22 144 (incorporated by reference), especiallypage 2 lines 44 to 67, DE-A 196 29 053 (incorporated by reference),especially page 2 line 51 to page 3 line 29, U.S. Pat. No. 5,760,145(incorporated by reference), especially column 2 line 46 to column 4line 23 and U.S. Pat. No. 6,265,497 (incorporated by reference),especially column 2 lines 3 to 47.

The organopolysiloxanes (A) preferably possess an average viscosity offrom 100 to 10 000 mPa·s at 25° C.

Examples of hydrocarbon radicals R⁵ are alkyl radicals, such as themethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl,n-pentyl, isopentyl, neopentyl, tert-pentyl radical, hexyl radicals,such as the n-hexyl radical, heptyl radicals, such as the n-heptylradical, octyl radicals, such as the n-octyl radical and isooctylradicals, such as the 2,2,4-trimethylpentyl radical, nonyl radicals,such as the n-nonyl radical, decyl radicals, such as the n-decylradical, dodecyl radicals, such as the n-dodecyl radical, and octadecylradicals, such as the n-octadecyl radical; cycloalkyl radicals, such ascyclopentyl, cyclohexyl, cycloheptyl radicals and methylcyclohexylradicals, aryl radicals, such as the phenyl, naphthyl, anthryl andphenanthryl radical; alkaryl radicals, such as o-, m-, p-tolyl radicals,xylyl radicals and ethylphenyl radicals, and aralkyl radicals, such asthe benzyl radical, the α- and the β-phenylethyl radical.

Examples of radicals R⁶ are alkenyl radicals, such as the vinyl,5-hexenyl, allyl, 3-butenyl and 4-pentenyl radical; and alkynylradicals, such as the ethynyl, propargyl and 1-propyne radical.

As organosilicon compounds (B) which contain Si-bonded hydrogen atoms itis preferred to use linear, cyclic or branched organopolysiloxanescomprising units of the general formula $\begin{matrix}{{R_{e}^{5}H_{f}{SiO}_{\frac{4 - e - f}{2}}},} & (X)\end{matrix}$where

-   R⁵ is as defined above,-   e is 0, 1, 2 or 3,-   f is 0, 1 or 2-   and the sum of e+f is 0, 1, 2 or 3,-   with the proviso that there are on average at least two Si-bonded    hydrogen atoms.

The organosilicon compounds (B) preferably contain at least threeSi-bonded hydrogen atoms.

As organosilicon compounds (B) it is more preferred to useorganopolysiloxanes of the general formulaH_(h)R⁵ _(3-h)SiO(SiR⁵ ₂O)_(o)(SiR⁵HO)_(p)SiR⁵ _(3-h)H_(h)  (XI)where

-   R⁵ is as defined above,-   h is 0, 1 or 2,-   o is 0 or an integer from 1 to 1500, and-   p is 0 or an integer from 1 to 200,-   with the proviso that there are on average at least 2 Si-bonded    hydrogen atoms.

In the context of this invention formula (XI) is to be understood tomean that o units —(SiR⁵ ₂O)— and p units —(SiR⁵HO)— may be distributedarbitrarily in the organopolysiloxane molecule.

Examples of such organopolysiloxanes are, in particular, copolymerscomprising dimethylhydrosiloxane, methylhydrosiloxane, dimethylsiloxaneand trimethylsiloxane units, copolymers comprising trimethylsiloxane,dimethylhydrosiloxane and methylhydrosiloxane units, copolymerscomprising trimethylsiloxane, dimethylsiloxane and methylhydrosiloxaneunits, copolymers comprising methylhydrosiloxane and trimethylsiloxaneunits, copolymers comprising methylhydrosiloxane, diphenylsiloxane andtrimethylsiloxane units, copolymers comprising methylhydrosiloxane,dimethylhydrosiloxane and diphenylsiloxane units, copolymers comprisingmethylhydrosiloxane, phenylmethylsiloxane, trimethylsiloxane and/ordimethylhydrosiloxane units, copolymers comprising methylhydrosiloxane,dimethylsiloxane, diphenylsiloxane, trimethylsiloxane and/ordimethylhydrosiloxane units, and copolymers comprisingdimethylhydrosiloxane, trimethylsiloxane, phenylhydrosiloxane,dimethylsiloxane and/or phenylmethylsiloxane units.

As organosilicon compounds (B) it is also possible to use those asdescribed in U.S. Pat. No. 5,691,435 (incorporated by reference),especially column 3 line 45 to column 4 line 29.

The organopolysiloxanes (B) preferably possess an average viscosity offrom 10 to 1 000 mPa·s at 25° C.

Organosilicon compound (B) is used preferably in amounts of from 0.5 to3.5, more preferably from 1.0 to 3.0, gram atoms of Si-bonded hydrogenper mole of Si-bonded radical containing aliphatic carbon-carbonmultiple bond in the organosilicon compound (A).

In the case of the crosslinkable silicone coating compositions as wellit is possible, as catalysts which promote the addition of Si-bondedhydrogen onto aliphatic multiple bonds, to use the same catalysts whichit has also been possible to use to date to promote the addition ofSi-bonded hydrogen onto aliphatic multiple bond. As constituent (C) itis preferred to use the abovementioned catalysts (3).

The catalysts (C) are used preferably in amounts of from 10 to 1000 ppmby weight (parts by weight per million parts by weight), more preferablyfrom 50 to 200 ppm by weight, calculated in each case as elementalplatinum metal and based on the overall weight of the organosiliconcompounds (A) and (B).

The crosslinkable silicone coating compositions may comprise agentswhich retard the addition of Si-bonded hydrogen onto aliphatic multiplebond at room temperature, known as inhibitors (D).

For the crosslinkable silicone coating compositions as well it ispossible as inhibitors (D) to use all inhibitors which it has also beenpossible to use to date for the same purpose.

Examples of inhibitors (D) are1,3-divinyl-1,1,3,3-tetramethyldisiloxane, benzotriazole,dialkylformamides, alkylthioureas, methyl ethyl ketoxime, organiccompounds or organosilicon compounds having a boiling point of at least25° C. at 1012 mbar (abs.) and containing at least one aliphatic triplebond, such as 1-ethynylcyclohexan-1-ol, 2-methyl-3-butyn-2-ol,3-methyl-1-pentyn-3-ol, 2,5-dimethyl-3-hexyne-2,5-diol and3,5-dimethyl-1-hexyn-3-ol, 3,7-dimethyloct-1-yn-6-en-3-ol, a mixture ofdiallyl maleate and vinyl acetate, maleic monoesters, and inhibitorssuch as the compound of the formula HC≡C—C(CH₃) (OH)—CH₂—CH₂—CH═C(CH₃)₂,available commercially under the trade name “Dehydrolinalool” from BASF.

Where inhibitor (D) is used, it is employed appropriately in amounts ofpreferably from 0.01 to 10% by weight, more preferably from 0.01 to 3%by weight, based on the overall weight of the organosilicon compounds(A) and (B).

Examples of further constituents which may be used in the crosslinkablesilicone coating compositions are agents for adjusting the releaseforce, organic solvents, adhesion promoters, and pigments.

Examples of agents for adjusting the release force of the coatings,repellent to tacky substances, that are produced with the compositionsof the invention are silicone resins comprising units of the formulaR⁷R⁵ ₂SiO_(1/2) and SiO₂,known as MQ resins, where R⁷ is a hydrogen atom, a hydrocarbon radicalR⁵, such as methyl radical, an alkenyl radical R⁶, such as vinylradical, and R⁵ and R⁶ are as defined above, and the units of theformula R⁷R⁵ ₂SiO_(1/2) may be identical or different. The ratio ofunits of the formula R⁷R⁵ ₂SiO_(1/2) to units of the formula SiO₂ ispreferably from 0.6 to 2. The silicone resins are used preferably inamounts of from 5 to 80% by weight, based on the overall weight of theorganosilicon compounds (A) and (B).

Examples of organic solvents are petroleum spirits, e.g., mixtures ofalkanes having a boiling range of from 70° C. to 180° C., n-heptane,benzene, toluene and xylenes, halogenated alkanes having from 1 to 6carbon atoms, such as methylene chloride, trichloroethylene andperchloroethylene, ethers, such as di-n-butyl ether, esters, such asethyl acetate, and ketones, such as methyl ethyl ketone andcyclohexanone.

Where organic solvents are used, they are employed appropriately inamounts of preferably from 10 to 90% by weight, more preferably from 10to 70% by weight, based on the overall weight of the organosiliconcompounds (A) and (B).

Although the sequence when mixing the constituents (X), (A), (B), (C)and, where used, (D) is not critical, it has nevertheless been foundappropriate for practical purposes to add constituent (C), viz thecatalyst, last to the mixture of the other constituents.

The crosslinking of the compositions of the invention takes placepreferably at from 70° C. to 180° C. As energy sources for thermalcrosslinking it is preferred to use ovens, e.g., forced air dryingovens, heating tunnels, heated rollers, heated plates, or heat rays fromthe infrared region.

As well as thermally, the compositions of the invention may also becrosslinked by irradiation with ultraviolet light or by irradiation withUV and IR light. As ultraviolet light it is common to use that having awavelength of 253.7 nm. In commerce there are a large number of lampswhich emit ultraviolet light having a wavelength of from 200 to 400 nmand which preferentially emit ultraviolet light having a wavelength of253.7 nm.

The invention further provides shaped bodies produced by crosslinkingthe compositions of the invention.

The shaped bodies preferably comprise coatings, more preferably coatingswhich repel tacky substances.

The invention further provides a process for producing coatings byapplying crosslinkable compositions of the invention to the surfacesthat are to be coated and then crosslinking the compositions.

The crosslinkable compositions of the invention are used preferably forproducing coatings which repel tacky substances, e.g., for producingrelease papers. Coatings which repel tacky substances are produced byapplying crosslinkable compositions of the invention to the surfacesthat are to be made repellent to tacky substances and then crosslinkingthe compositions.

The application of the compositions of the invention to the surfaces tobe coated, preferably surfaces to be made repellent to tacky substances,may be accomplished in any desired manner which is suitable and widelyknown for the production of coatings from liquid materials; for example,by dipping, brushing, pouring, spraying, rolling, printing, by means ofan offset gravure coating apparatus, for example, blade or knifecoating, or by means of an airbrush.

The coat thickness on the coated surfaces is preferably from 0.3 to 6μm, with particular preference from 0.5 to 2.0 μm.

The surfaces to be coated, preferably surfaces to be made repellent totacky substances, which may be treated in the context of the inventionmay be surfaces of any materials which are solid at room temperature and1012 mbar (abs.). Examples of surfaces of this kind are those of paper,wood, cork, and polymer films, e.g., polyethylene films or polypropylenefilms, woven and nonwoven fabric of natural or synthetic fibers, ceramicarticles, glass, including glass fibers, metals, polyethylene-coatedpaper, and boards, including those of asbestos. The abovementionedpolyethylene may in each case be high-pressure, medium-pressure orlow-pressure polyethylene. In the case of paper the paper in questionmay be of a low-grade kind, such as absorbent papers, including kraftpaper which is in the raw state, i.e., has not been pretreated withchemicals and/or natural polymeric substances, and which has a weight offrom 60 to 150 g/m², unsized papers, papers of low freeness value,mechanical papers, unglazed or uncalendered papers, papers which aresmooth on one side owing to the use of a dry glazing cylinder duringtheir production, without additional complex measures, and which aretherefore referred to as “machine-glazed papers”, uncoated papers orpapers produced from waste paper, i.e., what are known as recycledpapers. The paper to be treated in accordance with the invention mayalso of course, however, comprise high-grade paper types, such aslow-absorbency papers, sized papers, papers of high freeness value,chemical papers, calendered or glazed papers, glassine papers,parchmentized papers or precoated papers. The boards as well may be ofhigh or low grade.

The compositions of the invention are suitable, for example, forproducing release, backing, and interleaving papers, includinginterleaving papers which are employed in the production of, forexample, cast films or decorative films, or of foam materials, includingthose of polyurethane. The compositions of the invention are alsosuitable, for example, for producing release, backing, and interleavingcards, films, and cloths, for treating the reverse sides ofself-adhesive tapes or self-adhesive sheets or the written faces ofself-adhesive labels. The compositions of the invention are additionallysuitable for treating packing material, such as that comprising paper,cardboard boxes, metal foils and drums, e.g., cardboard, plastic, woodor iron, which is intended for storing and/or transporting tacky goods,such as adhesives, sticky foodstuffs, e.g., cakes, honey, candies, andmeat; bitumen, asphalt, greased materials, and crude rubber. A furtherexample of the application of the compositions of the invention is thetreatment of carriers for transferring pressure-sensitive adhesive filmsin the context of what is known as the transfer process.

The crosslinkable silicone coating compositions comprising theantimisting additives of the invention are especially suitable for usein rapid coating systems with coating speeds of preferably from 300 to2000 m/min, more preferably from 400 to 1500 m/min, in which thecompositions of the invention are applied at high speeds to the surfacesthat are to be coated.

The compositions of the invention are suitable for producing theself-adhesive materials joined to the release paper, both by the offlinemethod and by the inline method.

In the offline method, the silicone composition is applied to the paperand crosslinked, and then, in a subsequent stage, normally after thewinding of the release paper onto a roll and after the storage of theroll, an adhesive film, present for example on a label face paper, isapplied to the coated paper and the composite is then compressed. In theinline method the silicone composition is applied to the paper andcrosslinked, the silicone coating is coated with the adhesive, the labelface paper is then applied to the adhesive, and the composite, finally,is compressed.

In the case of the offline method the winding speed is governed by thetime needed to render the silicone coating tack-free. In the case of theinline method the process speed is governed by the time needed to renderthe silicone coating migration-free. With the compositions of theinvention the offline method and the inline method can be operated atspeeds from 300 to 2000 m/min, preferably from 400 to 1500 m/min.

1. Preparation of the Alkenyl-Functional Siloxane Copolymers:

EXAMPLE 1

At 25° C. 683 g of an α,ω-dihydrosiloxane of average chain length Si₂₂₅and 7.72 g of trivinylcyclohexane are dissolved in 1036 g of toluene(C═C/SiH=1.74) and with thorough stirring a quantity of a 1% strength(based on elemental platinum) solution of aplatinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in anα,ω-divinyldimethylpolysiloxane having a viscosity of 1000 mPa·s at 25°C. (a solution of the catalyst known as the Karstedt catalyst, whosepreparation is described in U.S. Pat. No. 3,775,452) is added such thatthe solution contains 10 ppm platinum. Over the course of 4 h at 30° C.the viscosity becomes very much greater until finally 3900 mm²/s (25°C.) are reached. 2072 g of divinyl-terminated polydimethylsiloxane with200 mm²/S (25° C.) are added and the toluene is removed in vacuo. Theresulting product has a viscosity of 7300 mm²/S (25° C.).

EXAMPLE 2

At 25° C. 683 g of an α,ω-dihydrosiloxane of average chain length Si₂₂₅and 7.72 g of trivinylcyclohexane are dissolved in 1036 g of toluene(C═C/SiH=1.74) and with thorough stirring an amount of the Karstedtcatalyst described in example 1 is added such that the solution contains10 ppm platinum. Over the course of 4 h at 30° C. the viscosity becomesvery much greater until finally 3900 mm²/s (25° C.) are reached. 1036 gof trimethylsilyl-terminated polydimethylsiloxane with 9.8 mm²/s (25°C.) are added and the toluene is removed in vacuo and replaced by thesame amount of 1-dodecene. This gives a solution of a vinyl-functionalbranched siloxane polymer in 1-dodecene, with a viscosity of 4380 mm²/S(25° C.).

EXAMPLE 3

At 25° C. 683 g of an α,ω-dihydrosiloxane of average chain length Si225and 7.72 g of trivinylcyclohexane are dissolved in 1036 g of toluene(C═C/SiH=1.74) and with thorough stirring an amount of the Karstedtcatalyst described in example 1 is added such that the solution contains10 ppm platinum. Over the course of 4 h at 30° C. the viscosity becomesvery much greater until finally 3900 mm²/s (25° C.) are reached. 1036 gof trimethylsilyl-terminated polydimethylsiloxane with 9.8 mm²/s (25°C.) are added and the toluene is removed in vacuo. The resulting producthas a viscosity of 11 600 mm²/s (25° C.).

EXAMPLE 4

492 g of an α,ω-dihydrosiloxane of average chain length Si_(50.2) aremixed homogeneously with 24.5 g of trivinyl-cyclohexane (C═C/SiH=1.70)and 516.5 g of toluene and the mixture is activated with 3 mg ofplatinum, added in the form of the Karstedt catalyst solution describedin example 1. The mixture is stirred at 80° C. for 2 h and then 515 g of1-dodecene are added and the toluene is removed under reduced pressure.This gives a 50% strength solution of a vinyl-functional branchedsiloxane polymer in 1-dodecene with a viscosity of 275 mm²/s (25° C.).

EXAMPLE 5

492 g of an α,ω-dihydrosiloxane of average chain length Si_(14.9) aremixed homogeneously with 80.5 g of trivinyl-cyclohexane (C═C/SiH=1.65)and 573 g of a trimethyl-silyl-terminated polydimethylsiloxane ofviscosity 9.8 mm²/s (25° C.) and the mixture is activated with 3 mg ofplatinum, added in the form of the Karstedt catalyst solution describedin example 1. After heating up independently, the mixture is held at 80°C. for 1 h and then cooled. This gives a 50% strength solution of avinyl-functional branched siloxane polymer with a viscosity of 660 mm²/s(25° C.).

EXAMPLE 6

592 g of an α,ω-dihydrosiloxane of average chain length Si_(14.9) aremixed with 83 g of trivinylcyclohexane (C═C/SiH=1.70) and the mixture isactivated with 3 mg of platinum, added in the form of the Karstedtcatalyst solution described in example 1. The reaction mixture attains110° C. in about 3 minutes and at the same time becomes considerablymore viscous. Removal of volatiles gives a clear oil with a viscosity of9400 mm²/s at 25° C. It contains Si—C-bonded α-olefinic double bonds,which can be hydrosilylated.

2. Use of the Alkenyl-Functional Siloxane Copolymers as AntimistingAdditives:

EXAMPLE 7

The alkenyl-functional siloxane copolymers of the invention are used,for reducing the formation of aerosol, as additives in crosslinkablesilicone coating systems for use in rapid coating processes.

The standard formulation used was a mixture of

-   100 parts by weight of a linear α,ω-divinyl-dimethylpolysiloxane,    having a viscosity of 300 mPa·s (25° C.),-   3.1 parts by weight of a linear polysiloxane comprising    hydromethylsiloxane and dimethylsiloxane units in a molar ratio of    2:1 having trimethylsiloxane end units and a viscosity of 34 mPa·s    (25° C.),-   1.25 parts by weight of a 1% strength by weight (based on elemental    platinum) solution of a    platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in an    α,ω-divinyldimethylpolysiloxane having a viscosity of 1000 mPa·s at    25° C., and-   0.3 part by weight of 1-ethynylcyclohexanol.

The additives of the invention from the preparation examples indicatedin table 1 were added to the standard formulation in the amountsspecified in table 1. As a control, a standard formulation withoutinventive additive was used. These mixtures were used for coating paper.

The substrate used was paper from Ahlstrom bearing the designationGlassine Larice Tipo 325, 62 g/m². Coating was carried out on the “BMBPilotplant” coating unit from Bachofen & Meier AG, having a 5-rollapplicator unit, at 550 m/min. The application roller was run at 95% ofthe paper speed. The coating was cured in a drying oven with a length of18 m at 160° C. This corresponds to a crosslinking time of 1.96 seconds.

The formation of aerosol was determined using the Dusttrak AerosolMonitor Model 8520. Samples were taken between the silicone applicationroll and the roll nip at a distance of 12 cm from the siliconeapplication roll.

The blank aerosol value prior to the coating tests was between0.028-0.031 mg/m³. During the coating tests, the minimum and maximumindicated aerosol levels were recorded and the average was calculated.The average aerosol levels measured during the coating tests werecorrected by the blank value of 0.03 mg/m³ in order to determine theeffect due purely to the antimisting additives of the invention.

The coating weight was determined by means of x-ray fluorescenceanalysis in reference to an appropriate standard.

Since the extent of aerosol formation is dependent among other things onthe coating weight, the average calculated aerosol levels werestandardized to a coating weight of 1 g/m² for the purpose of bettercomparability.

The effect of the antimisting additives of the invention on the curingof the coating system was determined immediately by means of a migrationtest and in parallel by means of extraction of uncrosslinked fractionsin MIBK (methyl isobutyl ketone).

The migration is assessed according to its extent using the marks 1 to6, mark 1 meaning no migration (complete curing), mark 3 slight and mark6 severe migration (incomplete curing).

The effect of the antimisting additives of the invention on the adhesionof the coating system to the substrate was determined by means of aruboff test. The abrasion is assessed according to its extent using themarks 1 to 6, mark 1 meaning no abrasion, mark 3 slight and mark 6severe abrasion.

The test methods are described in the brochure DEHESIVE® Silicones TestMethods from Wacker-Chemie GmbH. The results are summarized in table 1.TABLE 1 Average misting [mg/m³] Extract Amount Misting [mg/m³]standardized to [%] in Additive [%] min. max. av. 1.0 g/m² MigrationAbrasion MIBK Ex. 2 5 0.674 1.372 0.967 0.65 1 2 3.9 Ex. 1 8 0.504 0.9890.687 0.42 1 1 5.3 — — 19.47 30.17 24.27 16.51 1 2 3.9

The examples in comparison with the control test without additive showthat the addition of the antimisting additives of the inventionsignificantly reduces the formation of aerosol by crosslinkable siliconecoating systems in rapid coating processes.

Deleterious effects on migration and substrate adhesion (abrasion) arenot observed; within the bounds of measurement accuracy, the proportionof the extractable fractions is not increased.

EXAMPLE 8

At a high application weight and with certain coating formulations,aerosol may be formed even at machine speeds well below 500 m/min. Thealkenyl-functional siloxane copolymers of the invention were used, forreducing the formation of aerosol, as additives in crosslinkablesilicone coating systems for use in such coating processes.

The standard formulation used was a mixture of

-   100 parts by weight of a branched polysiloxane containing    vinyldimethylsiloxy end groups, having a viscosity of 420 mPa·s (25°    C.) and an iodine number of 8.0, prepared in accordance with Example    3 of U.S. Pat. No. 6,034,225,-   3.6 parts by weight of a linear polysiloxane comprising    hydromethylsiloxane and trimethylsiloxane units in a molar ratio of    24:1,-   1.04 parts by weight of a 1% strength by weight (based on elemental    platinum) solution of a    platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex in an    α,ω-divinyldimethylpolysiloxane having a viscosity of 1000 mPa·s at    25° C., and-   0.3 part by weight of 1-ethynylcyclohexanol.

The additives of the invention from the preparation examples indicatedin table 2 were added to the standard formulation in the amountsspecified in table 2. As a control, a standard formulation withoutinventive additive was used. These mixtures were used for coating paper.

The substrate used was paper from Ahlstrom bearing the designationGlassine Larice Tipo 325, 62 g/m². Coating was carried out on the pilotcoating unit from Dixon with the model number 1060, having a 5-rollapplicator unit, at 150 m/min. The application roller was run at 95% ofthe paper speed. The coating was cured in a drying oven with a length of3 m at 140° C.

The formation of aerosol was determined using the Dusttrak AerosolMonitor Model 8520. Samples were taken between the silicone applicationroll and the roll nip at a distance of 12 cm from the siliconeapplication roll. Additionally, the formation of aerosol was assessedvisually and evaluated with the codes 1-3:

-   -   1 no visible aerosol formation    -   2 slightly visible aerosol formation    -   3 severe aerosol formation.

During the coating experiments, the maximum indicated aerosol levelswere recorded. The coating weight was determined by means of X-rayfluorescence analysis in reference to an appropriate standard, and was 4g/m².

Furthermore, the effect of the antimisting additives according to theinvention on the curing of the coating system was determined by means ofa migration test. The migration test is described in the brochureDEHESIVE® Silicones Test Methods from Wacker-Chemie GmbH.

The results are summarized in table 2. TABLE 2 Amount of Misting,additive mg/m³ Misting Additive in % (Dusttrak) (visual) MigrationExample 6 2 3.5 1 1.5 Example 5 4 4 1 1 Example 4 4 7.5 1.5 1.5 Example3 5 3 1 1.5 Example 2 4 3.5 1.5 2 Example 1 8 2.5 1.5 1.5 — — 17 3 2

The comparative experiments show that the addition of the branchedorganosilicon compound of the invention, as antimisting additivesmarkedly reduces the formation of aerosol by crosslinkable siliconecoating systems in rapid coating processes.

Example 9 and comparative test as per EP-A 716 115:

An important criterion for the simple usefulness of antimistingadditives in curable compositions is their miscibility with thesecompositions.

In order to obtain reproducible results when curing on the coatingmachine, it is advantageous if the additive can be dispersedhomogeneously in the desired amount in the curable composition withoutunduly great effort, and forms a clear formulation. Accordingly, 104.4 gof the standard formulation from Example 7 are mixed with 10 g of eachof the additives from preparation examples 1 to 6 by moderate stirringusing a glass rod, so that a ready-to-use formulation is formed within afew minutes. All formulations are homogeneous, clear, and free fromstreaks.

For comparison, in accordance with the state of the art, an antimistingadditive as per EP-A 716 115 is prepared:

A mixture of 34 g of 2-methyl-3-buten-2-ol and 190 g of an allylpolyether of the formula CH₂═CH—CH₂O(C₂H₄O)_(9.4)H is mixed with 200 gof a siloxane having trimethylsiloxy end groups and comprisinghydromethylsiloxane and dimethylsiloxane units (0.30% by weight activehydrogen, viscosity 37 mm²/s at 25° C.), and the mixture is heated to50° C. and activated with 20 ppm platinum in the form of the platinumcatalyst described in Example 8 (Karstedt catalyst). After 2 hours, theexothermic reaction gives a clear product with an active hydrogencontent of less than 0.002% by weight and a slight brown coloration.Stirring 10 g of this product into 104.4 g of the standard formulationfrom Example 7 gives a milky mixture which shows severe phase separationafter 4 hours of storage. Even when only 5 g of this additive is mixedin under strong shearing with a Turrax® device, a clear formulation isnot obtained.

1-14. (canceled)
 15. In a process for the coating of substrates withcrosslinkable silicone(s) wherein an antimisting additive is employedfor reducing the formation of aerosol, the improvement comprisingselecting as at least one antimisting additive, an alkenyl-functionalsiloxane copolymer comprising (a) siloxane units of the formula$\begin{matrix}{R_{a}{{Si}\left( {OR}^{1} \right)}{{}_{}^{}{}_{{4 - \left( {a + b} \right)}2}^{}}} & (I)\end{matrix}$ where each R independently is an identical or different,optionally halogenated hydrocarbon radical having from 1 to 18 carbonatoms per radical, R¹ each is an identical or different alkyl radicalhaving from 1 to 4 carbon atoms per radical, optionally substituted byan ether oxygen atom, a is 0, 1, 2 or 3, b is 0, 1, 2 or 3 and the suma+b is not greater than 3, (b) per molecule at least one siloxane unitof the formula $\begin{matrix}{{A{Si}R}_{c}{SiO}_{\frac{4 - {({c + 1})}}{2}}} & ({II})\end{matrix}$ where c is 0, 1 or 2, A is a radical of the formula—CH₂CHR³—R²(CR³═CH₂)_(x-1) where R² is a divalent, trivalent ortetravalent hydrocarbon radical having from 1 to 25 carbon atoms perradical, R³ is a hydrogen atom or an alkyl radical having from 1 to 6carbon atoms per radical, and x is 2, 3 or 4, and (c) per molecule onaverage at least one unit selected from the group consisting of units ofthe formulae $\begin{matrix}{{{O_{\frac{4 - {({c + 1})}}{2}}R_{c}{Si}} - A^{1} - {{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}},} & ({III}) \\\begin{matrix}{{{O_{\frac{4 - {({c + 1})}}{2}}R_{c}{Si}} - A^{2} - {{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}},} \\| \\{\quad{{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}}\end{matrix} & ({IV}) \\{\begin{matrix}{\quad{{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}} \\| \\{{O_{\frac{4 - {({c + 1})}}{2}}R_{c}{Si}} - A^{3} - {{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}} \\| \\{\quad{{{Si}R}_{c}O_{\frac{4 - {({c + 1})}}{2}}}}\end{matrix},} & (V)\end{matrix}$ where A¹ is a radical of the formula

where A² is a radical of the formula

with the proviso that R² is not a divalent hydrocarbon radical, and A³is a radical of the formula

with the proviso that R² is not a divalent or trivalent hydrocarbonradical.
 16. The process of claim 15, wherein the alkenyl-functionalsiloxane copolymer comprises (a) siloxane units of the formulaR₂SiO  (I′), (b) per molecule on average more than one siloxane unit ofthe formulaAR₂SiO_(1/2)  (II′) and (c) per molecule on average at least one unitselected from the group consisting of units of the formulae


17. The process of claim 15, wherein the radical R³ is a hydrogen atom.18. In a process for the coating of substrates with crosslinkablesilicone(s) wherein an antimisting additive is employed for reducing theformation of aerosol, the improvement comprising selecting as at leastone antimisting additive an alkenyl-functional siloxane copolymerprepared by reacting at least one organic compound (1) containing atleast two aliphatic double bonds, of the formulaR²(CR³═CH₂)_(x), where each R² is independently a divalent, trivalent ortetravalent hydrocarbon radical having from 1 to 25 carbon atoms perradical, R³ each independently is a hydrogen atom or an alkyl radicalhaving from 1 to 6 carbon atoms per radical, and x is 2, 3 or 4, with atleast one organopolysiloxane (2) having on average more than oneSi-bonded hydrogen atom per molecule, in the presence of ahydrosilylation catalyst (3), the ratio of aliphatic double bonds inorganic compound (1) to Si-bonded hydrogens in the organopolysiloxane(2) being such that alkenyl-functional siloxane copolymers comprising onaverage more than one alkenyl group per molecule, of the formula—CR³═CH₂, are obtained.
 19. The process of claim 18, wherein saidorganic compound (1) comprises 1,2,4-trivinylcyclohexane.
 20. Theprocess of claim 18, wherein at least one organopolysiloxane (2) has theformulaHR₂SiO(SiR₂O)_(o)SiR₂H where each R independently is an identical ordifferent or different, optionally halogenated C₁₋₁₈ hydrocarbonradical, and o is an integer from 50 to
 1000. 21. The process of claim18, wherein the ratio of aliphatic double bonds in organic compound (1)to Si-bonded hydrogens in organopolysiloxane (2) is from 1.5:1 to 3.0:1.22. The process of claim 15, wherein said crosslinkable silicone coatingcomposition comprises (A) at least one organosilicon compound bearingradicals containing one or more aliphatic carbon-carbon multiple bonds,said organosilicon compound different from said antimisting additive,(B) at least one organosilicon compound containing Si-bonded hydrogenatoms, (C) at least one hydrosilylation catalyst, and optionally, (D)one or more inhibitors.
 23. The process of claim 18, wherein saidcrosslinkable silicone coating composition comprises (A) at least oneorganosilicon compound bearing radicals containing one or more aliphaticcarbon-carbon multiple bonds, said organosilicon compound different fromsaid antimisting additive, (B) at least one organosilicon compoundcontaining Si-bonded hydrogen atoms, (C) at least one hydrosilylationcatalyst, and optionally, (D) one or more inhibitors.
 24. Acrosslinkable silicone coating composition with reduced aerosolformation, comprising (X) at least one antimisting additive as definedin claim 15, (A) at least one organosilicon compound having radicalscontaining one or more aliphatic carbon-carbon multiple bonds, saidorganosilicon compound different from (X), (B) at least oneorganosilicon compound containing Si-bonded hydrogen atoms, (C) at leastone hydrosilylation catalyst, and optionally, (D) one or moreinhibitors.
 25. A crosslinkable silicone coating composition withreduced aerosol formation, comprising (X) at least one antimistingadditive as defined in claim 18, (A) at least one organosilicon compoundhaving radicals containing one or more aliphatic carbon-carbon multiplebonds, said organosilicon compound different from (X), (B) at least oneorganosilicon compound containing Si-bonded hydrogen atoms, (C) at leastone hydrosilylation catalyst, and optionally, (D) one or moreinhibitors.
 26. A shaped body produced by crosslinking the compositionof claim
 24. 27. The shaped body of claim 26, which is a coating. 28.The shaped body of claim 26, which is a release coating for tackysubstances.
 29. A process for producing coatings with reduced aerosolformation during the coating process, comprising applying thecrosslinkable composition of claim 24 to a surface to be coated, andcrosslinking the crosslinkable composition.
 30. A process for producinga release coating for tacky substances, comprising applying acrosslinkable composition of claim 24 to a surface desired to haverelease properties for tacky substances, and crosslinking thecomposition.